Yeast pheromone could revolutionize control of Helicoverpa armigera

The plague is expensive. Helicoverpa armigera, known as the cotton bollworm or armigera caterpillar, causes immense global damage. Resistant to several insecticides and capable of attacking more than 180 plants, it has become a challenge for modern agriculture. But a new study conducted in Greece proposes an innovative solution: the use of pheromones produced by yeast, applied in the field by drones.

The method is called “mating disruption.” It involves spreading chemical substances similar to those released by female insects to attract males into the environment. This causes the insect to lose the ability to locate its mate, reducing reproduction. The technique is not new. What has changed is how this pheromone is produced and applied.

For three consecutive years, researchers tested this approach in cotton fields in the Spercheios Valley in Central Greece. The study compared the effectiveness of traditional, chemically derived pheromones with yeast-biosynthesized pheromones. Both were embedded in a biodegradable paraffin-based matrix called PheroWax.

The results were impressive. In all harvests, the use of yeast pheromones reduced the capture of males in traps by more than 99%. In 2020, the traps in treated fields did not capture a single male. In 2021, even with the pest population on the rise, the reproductive blockade remained effective. In the third year, yeast pheromones were used in larger fields, with 7 hectares. Once again, the number of captures dropped to almost zero.

The pheromone was released both manually and with drones adapted to distribute the product bubbles. With the help of georeferenced maps, the UAVs flew over the fields and released the bubbles directly onto the plants. Application by drones ensured uniform distribution and reduced work time.

The choice of the PheroWax matrix was not accidental. The compound protects sensitive pheromone molecules from heat and UV light, in addition to releasing the active ingredient in a controlled manner for up to nine weeks. Since it is biodegradable, it does not require subsequent collection. This eliminates the need to dispose of plastics, such as those used in previous methods based on polyethylene microtubes.

The agricultural yield analysis was also positive. In 2022, fields treated with the new method produced 4000 kg of cotton per hectare, compared to 3700 kg/ha in control fields. In addition, infestation was lower: 3,3% compared to 4,4% in untreated areas. In 2020 and 2021, the results were similar.

The technology employs two main compounds: (Z)-11-hexadecenal and (Z)-9-hexadecenal. These aldehydes make up the sex pheromone of H. armigera and were produced by genetically modified yeast. The process dramatically reduces costs compared to traditional chemical synthesis.

The viability of biotechnological production paves the way for the method to be used in crops with lower commercial value, such as corn and soybeans — previously limited to pheromones due to economic unfeasibility. Furthermore, since the technique acts specifically on the target species, it is believed that it will not harm natural enemies and pollinators.

More information can be found at doi.org/10.3390/insects16050523